ADC is a key building block of modern signal/audio/video processing circuits and communication circuits. Comparators that compare the difference between input signals have been widely used in ADC, such as flash ADC and SAR ADC. A general dynamic comparator is dynamically switched between a reset phase and a comparing phase. The dynamic comparator may include a preamplifier circuit and a latch circuit. The preamplifier circuit is used to amplify input signals and apply its output signals to the latch circuit, so that the sensitivity of the comparator can be improved. The performance of a comparator can be evaluated based on power consumption and operating speed. In this regard, there is a need for a comparator with low power consumption and high speed operation.